Adhesion primers for encapsulating epoxies

Abstract

A copper plastic laminate is provided having a high bond strength. The copper is selected from the group consisting of copper and copper alloys and has on its surface a uniform glassy-like, substantially pore-free coating of copper phosphate. A plastic encapsulating material containing a mold release agent is adhesively bonded to the copper.

We claim: 
     
       1. A process of forming a metal plastic composite, comprising the steps of: a. selecting said metal from the group consisting of copper and copper alloys;   b. coating the surface of said metal with an adhesion primer comprising a substantially glassy-like, pore-free phosphate coating;   c. rinsing said metal;   d. drying said metal; and   e. adhesively bonding a plastic material comprising an epoxide resin and a mold release agent to the surface of the copper or copper alloy metal having said adhesion primer.   
     
     
       2. The process as in claim 1 including the step of selecting said plastic material from an epoxide resin formulated as a thermosetting encapsulating epoxy. 
     
     
       3. The process as in claim 1 including the step of adding inert fillers to said plastic material to provide dimensional stability. 
     
     
       4. The process as in claim 3 including the step of selecting said mold release agent from a group of low melting temperature organics. 
     
     
       5. The process as in claim 4 including the step of selecting said mold release agent from the group consisting of silicones, stearates and fatty acids. 
     
     
       6. The process as in claim 2 further including the step of forming said metal into a leadframe. 
     
     
       7. The process as in claim 6 further including the step of connecting an electrical or electronic component to said leadframe, whereby said component is encapsulated by said epoxide resin. 
     
     
       8. The process as in claim 1 wherein said step of coating the surface of said metal includes immersing said metal in a phosphoric acid solution of at least 8 percent concentration and containing from 3.5 grams per liter up to the solubility limit of a material selected from the group consisting of sodium dichromate and potassium dichromate and mixtures thereof for at least 2 seconds to form a substantially pore-free coating of copper phosphate, provided that when the concentration of phosphoric acid is increased, the minimum dichromate concentration is proportionately increased. 
     
     
       9. The process as in claim 1 wherein the coating step includes immersing said metal in a solution containing an organophosphonic acid and a chromate free oxidizing agent for at least 4 seconds to coat the surface of said metal with a compound of said organophosphonic acid.